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The first example of an inorganic-ligand supported iron(III) catalysed coupling of formic acid and amines to form formamides is reported. The pure inorganic catalyst (NH4)3[FeMo6O18(OH)6] (1), which consists of a central FeIII single-atomic core supported within a cycle-shaped inorganic ligand consisting of six MoVIO6 octahedra, shows excellent activity and selectivity, and avoids the use of complicated/commercially unavailable organic ligands. Various primary amines and secondary amines have been successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines has also been achieved for the first time. The Fe catalyst 1 can be reused several times without appreciable loss of activity.

Engineering photoredox-triggered chemical transformation via visible light has been an emerging area in organic synthesis. However, most of the well-established photocatalysts are based upon either transition metal complexes involved with noble metals and organic ligands or photosensitive organic dyes, the development of pure inorganic molecular photocatalysts that could provide better stability and durability is greatly retarded. Herein we discover that the Anderson polyoxometalate (POM) Na-4[NiMo6O18(OH)(6)] (1), which consists of pure inorganic framework built from a central Ni-II core supported by six (MoO6)-O-VI inorganic scaffold/ligands, can be used as a powerful photocatalyst. Upon irradiation with visible light (>400 nm), the compound can catalyze, in high efficiency, a wide range of reactions, including the oxidative cross-coupling reaction of chlorides with amines, as well as oxidation of chlorides using molecular oxygen, affording various imines, aldehydes, and ketones, respectively in high selectivity and good yields. Owing to the robust inorganic framework, this catalyst exhibits excellent stability during the catalysis and reusability with little loss of the catalytic activity, thus providing an alternative without use of complicated organic ligands and expensive noble metal-based photosensitizers.

A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.

Oxidation is a powerful methodology that is widely used for the production of fine chemicals and pharmaceutical intermediates, however, this process often involves the use of toxic reagents and harsh reaction conditions. Herein we report an efficient and eco-friendly way to promote the aerobic oxidation of organic halides to aldehydes/ketones and oxidative coupling of amines to imines using an inorganic-ligand supported iron catalyst 1a (NH4)3[FeMo6O18(OH)6] with O2 (1 atm) as the sole oxidant. 1a is synthesized directly from cheap and commonly available (NH4)6Mo7O24·4H2O and Fe2(SO4)3, which consist of a pure inorganic framework built from a central FeIII core supported by six MoVIO6 inorganic scaffolds. The iron catalyst 1a exhibits better activity towards a wide range of substrates in the catalytic oxidation of halides and amines, and the use of toxic oxidants and potentially air/moisture sensitive and complicated organic ligands that are not commercially available is avoided. Owing to the robust inorganic framework, 1a shows good stability and reusability and the catalytic oxidation of halides and amines could be readily scaled up to gram-scale with little loss of catalytic activity, demonstrating the great potential of inorganic-ligand supported catalysts in catalytic chemical transformation.

The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.

Formamides represent an abundant class of compounds in organic synthesis. They can be made efficiently by the direct catalytic coupling of methanol with amines in the presence of metal-based catalysts. However, these catalysts require complicated organic ligands, susceptible to oxidative self-degradation, restricting their practical applications. Here, we describe an inorganic ligand-supported chromium (III) catalyst, (NH4)3[CrMo6O18(OH)6], which consists of a central chromium (III) single-atomic core supported by a cycle-shaped inorganic ligand consisting of six MoVIO6 octahedra, shows excellent activity and selectivity. Various primary amines and secondary amines are successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines is also achieved. The chromium catalyst can be reused several times with little loss of the activity. Mechanistic insight is provided based on the observation of an intermediate and control experiments. Several catalytic methods for N-formylation of amines using noble metals or manganese pincer complexes are known. Here an air-stable and reusable chromium-based polyoxometalate is shown to catalyze the N-formylation of amines and diamines using methanol and hydrogen peroxide.

Herein, we divulge an efficient protocol for aerobic oxidation of alcohols with an inorganic-ligand supported iodine catalyst, (NH4)5[IMo6O24]. The catalyst system is compatible with a wide range of groups and exhibits high selectivity, and shows excellent stability and reusability, thus serving as a potentially greener alternative to the classical transformations.

Most state-of-art transition-metal catalysts usually require organic ligands, which are essential for controlling the reactivity and selectivity of reactions catalyzed by transition metals. However, organic ligands often suffer from severe problems including cost, toxicity, air/moisture sensitivity, and being commercially unavailable. Herein, we show a simple, mild, and efficient aerobic oxidation procedure of amines using inorganic ligand-supported non-precious metal catalysts 1, (NH4)(n)[MMo6O18(OH)(6)] (M=Cu2+; Fe3+; Co3+; Ni2+; Zn2+, n=3 or 4), synthesized by a simple one-step method in water at 100 degrees C, demonstrating that the catalytic activity and selectivity can be significantly improved by changing the central metal atom. In the presence of these catalysts, the catalytic oxidation of primary and secondary amines, as well as the coupling of alcohols and amines, can smoothly proceed to afford various imines with O-2 (1atm) as the sole oxidant. In particular, the catalysts1 have transition-metal ion core, and the planar arrangement of the six Mo-VI centers at their highest oxidation states around the central heterometal can greatly enhance the Lewis acidity of catalytically active sites, and also enable the electrons in the center to delocalize onto the six edge-sharing MO6 units, in the same way as ligands in traditional organometallic complexes. The versatility of this methodology maybe opens a path to catalytic oxidation through inorganic ligand-coordinated metal catalysis.